(a) Fields of the Invention
The present invention relates to insulating film formation methods employed for semiconductor devices, semiconductor devices, and substrate processing apparatus.
(b) Description of Related Art
In recent years, the wafer size of a semiconductor substrate has been enlarged and a semiconductor element design has become finer. With such trend, decreasing variations in processing dimensions among apparatus for mass production becomes important in order to improve the fabrication yield thereof. In particular, since the thickness uniformity of a gate insulating film or a capacitor insulating film affects variations in the characteristics of a device using this insulating film, it is desirable that the thickness uniformity of the insulating film, such as the uniformity within a wafer, the wafer-to-wafer uniformity, and the process-to-process uniformity, be good.
Since a device with a design rule of 100 nm or smaller is required to have an excellent thickness uniformity, a film formation made by an ALD (Atomic Layer Deposition) method, which is one of CVD (Chemical Vapor Deposition) methods, is employed. The ALD method is a film formation method carried out in the manner in which under a given film-formation condition (temperature and pressure), at least two or more types of material gases are supplied onto a wafer alternately, one type at a time, and resulting surface reaction thereon alone allows atoms of each type to adsorb by a single atomic layer (see, for example, Japanese Unexamined Patent Publication No. 2004-165668).
In the ALD method, however, a single atomic layer is formed on the wafer at a time, so that, for example, the processing time becomes longer. From such a fact, it is difficult for this method to respond to mass production of the device. To address this problem, a wafer processing apparatus called a vertical batch processing apparatus is developed within which 25 or more wafers each lie horizontally and are axially aligned within a reaction tube (see, for example, Japanese Unexamined Patent Publication No. 2006-66557).